The document discusses the history and development of atomic theory from Democritus' idea that matter is made of indivisible particles called atoms, to modern atomic structure and the periodic table of elements. It covers key contributors like Dalton, Thomson, Rutherford, and Bohr and their experiments that provided evidence for atoms and determined atomic structure, including the discovery of subatomic particles like electrons and the nuclear model of the atom. It also discusses applications of atomic and molecular spectroscopy.

1. The Atom Chapter 8 Great Idea: All of the matter around us is made of atoms, the chemical building blocks of our world

2. Chapter Outline The Smallest Pieces The Structure of the Atom When Matter Meets Light The Periodic Table of the Elements

3. The Smallest Pieces

4. The Smallest Pieces Democritus Cut matter to reach smallest piece Called “the atom” or “uncuttable” All material formed from atoms

5. Dividing a Bar of Gold

6. Elements John Dalton Father of modern atomic theory Cannot break down elements Elements composed of atoms Example: Water molecule is 1 oxygen atom and 2 hydrogen atoms

7. Envisioning Atoms

8. Are Atoms Real? Evidence for the reality of atoms Behavior of a gas Chemical combinations Radioactivity Brownian motion X-ray crystallography Atomic-scale microscopy

9. The Behavior of a Gas Bernoulli Atoms have mass and velocity and thus kinetic energy Decreasing volume increases pressure Increasing temperature increases pressure

10. The Behavior of Gases

11. Chemical Combinations Dalton applied law of definite proportions Elements combine in a specific ratio of weights Ex: Water is 8 parts oxygen to 1 part hydrogen

12. Chemical Combinations (cont.) Ratio of weights is a small whole number Ex: 12 lbs carbon can combine with either 16 lbs or 32 lbs of oxygen Implication: some units of elements are fundamentally indivisible

13. Radioactivity Radioactivity Discovered in 1896 Phosphors flash when hit by radiation 1903 demonstration of the twinkling caused by this effect

14. Brownian Motion Brownian motion: erratic, jiggling motion Pollen grains suspended in water Einstein: motion is random collisions of atoms Predicted particle movement Perrin tested and confirmed Einstein’s predictions

15. X-ray Crystallography Developed in 1912 Demonstrates arrangement of atoms in crystals

16. Discovering Chemical Elements Electrolysis Mendeleev Current periodic table 112 elements 92 found in nature

17. Helium, carbon, aluminum, copper, gold Everyday Elements

18. The Structure of the Atom

19. The Structure of the Atom Joseph Thomson identified electron Negatively charged Smaller and lighter than smallest atom Atoms are NOT fundamental building blocks, but are made up of smaller more fundamental particles

20. The Atomic Nucleus Ernest Rutherford determined atomic structure Concluded Atom has nucleus at center surrounded by electrons Later discoveries found nucleus is composed of protons and neutrons

21. Rutherford’s Experiment

22. Important Terms Related to Atoms

23. Why the Rutherford Atom Couldn’t Work Why? Object in circular orbit is accelerating Accelerated electrical charge emits electromagnetic radiation Electrons giving off energy while orbiting Result: electrons spin toward nucleus and eventually atom ceases to exist Rutherford atom exists <1min

24. The Nuclear Regulatory Commission Logo: highly stylized atomic model

25. When Matter Meets Light

26. Niels Bohr

27. The Bohr Atom First working model of atom Energy levels for electrons Specific distances from nucleus Electrons exist with no radiation Electrons cannot exist between allowed distances (energy levels)

28. Bohr Atom

29. Electron Energy Levels

30. Atomic Model

31. Photons: Particles of Light Photon absorbed Used to move electron to a higher energy state Photon emitted as electron moves to lower energy state

32. Photons: Particles of Light

33. Photons - cont. Quantum leap or jump -electron disappears from original location and reappears in final location- never at positions in between

34. Energy in Bohr Atom Energy required to leave ground state Absorb photon Heat Increases collisions

35. Spectroscopy Atoms emit and absorb different photons Depends on differences between energy levels Each atom has distinct set of photons Spectrum: all photons emitted by an atom Used for identification

36. Na, K, and Li – Give Distinctive Colors to a Flame

37. Spectroscopy – cont. Glass prism

38. Spectroscopy – cont. Line spectra for H, Na, and Ne

39. The Periodic Table of the Elements

40. The Science of Life Spectra of life’s chemical reactions Used to determine how enzymes work Used to identify pollutants emitted from automobile exhaust pipes

41. Science in the Making Helium Discovery Properties

42. Technology Lasers Produce a beam of light

43. Action of a Laser

44. Lasers Have Many Uses

45. Periodic Table of the Elements Systematizes elements Columns contain similar elements Alkali metals: soft, silvery metals Noble gases: colorless, odorless, and inert

46. Periodic Table of the Elements

47. Why the Periodic Table Works: Electron Shells Patterns mirror arrangement of electrons in shells Pauli exclusion principle First shell 2 electrons, second shell 8, etc.

48. Electron Representation